The present invention relates generally to air dryer assemblies, and more particularly to a twin tower type desiccator having two spin-on dryer cartridges each containing a volume of desiccant within a bag, and which includes a novel air-oil separator and valves which may be readily changed.
The unit has particular application in buses and railroad cars, as well as other applications wherein the duty cycle of the air compressor may be continuous. Another feature of the invention is ease of maintenance, so that little if any downtime is required. This is achieved by having spin-on cartridges, accessible valves and an oil separator which may be removed and replaced easily.
The unit operates, basically, by drying incoming compressed air in one cartridge while simultaneously regenerating the opposite cartridge with a portion of previously dried air. Control over the cycles is achieved with a so-called MLT (micro-logic timer) and associated valve which controls the cycling of the apparatus.
The reason for having dry air is that the air brake systems do not tolerate liquid water, nor even air which is relatively high in water vapor content. Consequently, it is highly desirable to use air that has been virtually completely dried. The problem of moisture in compressed air systems is well-known. It is known, for example that the reason that compressed air contains a great deal of moisture is that the process of compressing the air concentrates the same amount of moisture in a much smaller volume, thus raising the relative humidity of the compressed air.
Consequently, with air operating at a high degree of compression, there is a substantial increase in the relative humidity. If air, for example, is compressed at or above 200 psi, the relative amount of moisture therein can become very great. Accordingly, it is necessary when operating brakes or the like which have a requirement for dry air, to use some means of drying incoming or ambient air until its relative humidity is close to zero.
In addition to being dry, the air used in air brakes, for example, should be finely filtered to remove as many solid contaminants as possible, for obvious reasons, and should also contain means to separate oil from the air. Such an oil-air separator is a valuable feature of the present invention.
Accordingly, it is an object of the invention to provide an improved air dryer.
Another object is to provide such a unit with an air-oil separator of a novel design.
A still further object is to provide an air-oil separator which is disposed in unit so as to induce turbulent flow in incoming air, and to have the air undergo a direction-reversal before passing through a screen and filter on its way to the desiccant canisters.
Another object is to provide a pair of valves having small orifices therein through which air may flow even when these valves are closed, such air being used to pass in a reverse direction to strip moisture from, and thus regenerate, the desiccant cartridge.
Another object of the invention is to provide an air dryer having dual towers, each of which contains a desiccant in a cartridge of the spin-on variety of facilitate changing the desiccant when necessary.
Yet another object of the invention is to provide a cartridge which provides a filter for particulate materials and a tortuous path for the air which is to be directed to and through the desiccator.
Still another object of the invention is to provide an air dryer wherein the desiccant is contained in bags which are in turn contained in a cylindrical housing, which means the desiccant may be very finely subdivided for maximum effectiveness, and yet not be subject to leaking from its container.
A further object of the invention is to provide an air dryer containing twin towers in which, when one tower of the dryer is serving to dry incoming air, the other tower uses a minor portion of that air to regenerate the desiccant contained in the second tower.
Still another object of the invention is to provide a simplified, spin-on system of cartridge removal and replacement, which may be used only every year or two.
A further object of the invention is to provide a system wherein all essential elements of the air dryers are positioned so as to be readily available for maintenance, replacement, and/or repair.
A still further object of the invention is to provide a dual cartridge dryer which achieves economy and which is adaptable to specialty equipment and a large variety of other applications.
A further object of the invention is to provide an air-oil separator having a filter medium which is surface active and which therefore adsorbs oil and moisture, and which therefore can be regenerated by drier air passing over the separator in a reverse direction.
Yet another object of the invention is to provide a separator containing an aramid or equivalent adsorbing filter adhesively attached to a portion of the separator structure.
These and other objects and advantages of the present invention are achieved in practice by providing a dual cartridge desiccator system wherein air is subjected to oil separation by a novel device used in conjunction with a well or like housing for reversing the direction of air flow, adsorbing the oil in the air stream, passing the air through a filter and through the exterior of a desiccant cartridge, and thereafter passing it down and through the desiccant cartridge, and having it exit by way of a valve to an outlet port. The other cartridge is simultaneously regenerated by a controlled amount of bleed air entering the cartridge and flowing backwards through the desiccant contained in that cartridge and ultimately out a drain port controlled by a valve opened by air pressure. This operates the cycle in an opposite direction, all without causing an interruption or a loss of air pressure to the main supply.
The invention also achieves its objects by providing an electrically operated timer in the same device including a novel oil separator, whereby air pressure is directed to a control for an exhaust or purge valve for wet air and also to the inlet valve for air to be dried, while also providing certain auxiliary functions.
The manner in which the invention achieves its objects and other objects which are inherent in the invention will become more clearly apparent when reference is made to the following description of the preferred embodiments of the invention set forth by way of example and shown in the accompanying drawings in which like reference numbers indicate corresponding parts throughout.